CPF e CNPJ

CNP.java

public abstract class CNP {
    private final int   digits;
    private final int[] weight;
    
    public static final CNP CNPJ = new CNP(6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2) {
        public String format(String cnp) {
            cnp = normalize(cnp);
            return cnp.substring(0, 2) + "." + cnp.substring(2, 5) + "." + cnp.substring(5, 8) + "/" + cnp.substring(8, 12) + "-" + cnp.substring(12);
        };
    };
    public static final CNP CPF = new CNP(11, 10, 9, 8, 7, 6, 5, 4, 3, 2) {
        public String format(String cnp) {
            cnp = normalize(cnp);
            return cnp.substring(0, 3) + "." + cnp.substring(3, 6) + "." + cnp.substring(6, 9) + "-" + cnp.substring(9);
        };
    };

    private CNP(int... weight) {
        this.digits = weight.length + 1;
        this.weight = weight;
    }

    private int calculateNextDigit(String str) {
        int sum = 0;
        for (int i=0; i<str.length(); i++) {
            int digito = Integer.parseInt(str.substring(i,i+1));
            sum += digito*weight[weight.length-str.length()+i];
        }
        sum = 11 - sum % 11;
        return sum > 9 ? 0 : sum;
    }

    public String addDigits(String cnpPrefix) {
        cnpPrefix = normalize(cnpPrefix);
        if (cnpPrefix.length()!=digits-2) {
            throw new IllegalArgumentException("Expected number with " + (digits-2) + " digits, got " + cnpPrefix);
        }
        Integer digit1 = calculateNextDigit(cnpPrefix);
        Integer digit2 = calculateNextDigit(cnpPrefix + digit1);
        return cnpPrefix + digit1 + digit2;
    }

    public boolean isValid(String cnp) {
        if ((cnp==null) || (cnp.length()!=digits)) {
            return false;
        }
        return cnp.equals(addDigits(cnp.substring(0, digits-2)));
    }
    
    public String normalize(String cnp) {
        return cnp.replaceAll("[./- ]", "");
    }
    
    public abstract String format(String cnp);
}